1. Field of the Invention
This invention is concerned with a flyback converter having a transformer, having a primary winding and at least one secondary winding, wherein the primary winding is connected, in series and at least one secondary winding.
More specifically, the invention relates to a flyback converter wherein the primary winding is connected, in series supplies start pulses of a fixed frequency for the controlles switch, has a current sensor for the current through the primary winding. Coupled with the secondary winding is a first rectifying amplifier for comparing the amplifier for comparing the output current with an adjustable current reference value, wherein as a control signal the combined and decoupled output signals of the two rectifying amplifiers and the output signal of the current sensor of the actuation circuit are supplied for the purpose of influencing the pulse duty ratio, and the maximum output of the converter-primary part is lower than the product of the output voltage which can be adjusted to a maximum degree and the output current which can be adjusted to a maximum degree.
2. Description of the Related Art
Flyback converters are known and are widely used as mains power supply units for supplying current to electronic devices. For example, a known flyback converter is described as prior art in AT 403 535 B of the Applicant. A decisive cost factor for such mains power supply units is the power available to be drawn off since this, in particular, determines the costs for the transformer and smoothing means such as capacitors and throttles. A mains power supply unit of one construction type should, on the other hand, cover as many different applications as possible demanding different voltages and currents. For this reason mains power supply units are supplied with an adjustable voltage and adjustable current, for example a maximum of 30 volts, 3 amps. Within these limits the purchaser can then adjust the current and voltage, wherein as far as output is concerned the mains power supply unit, however, is fully used only at the highest voltage, in this case 30 volts.times.3 amps=90 watts. If, on the other hand, the purchaser adjusts the device to a low voltage, for example 3 volts, only a fraction of the power is available to him, namely in this example 3 volts.times.3 amps=9 watts. The device is not exploited according to its capabilities, in this case only to a tenth of its capability, and is unnecessarily expensive for the application concerned.